The present invention relates to the field of endovascular support to maintain patency of narrowed vessels and facilitate repair of injured or degenerated vessels by implantation of a device within the target vessel. More specifically, the invention relates to acceptable biological coverings for an endovascular support device and the local delivery of a therapeutic substance into the vascular tissue, as a complementary treatment.
Partial and even complete blockage of the vascular system by the formation of an atherosclerotic plaque is a well known and frequent medical problem. Such blockages are often treated with percutaneous transluminal coronary angioplasty (PTCA), also known as balloon angioplasty, or by intravascular stent implantation. PTCA is an alternative to vascular bypass surgery, which includes a surgically exposing incision, and removing, replacing, or bypassing the defective blood vessel. Structures which have previously been used as intraluminal vascular grafts have included coiled stainless steel springs, and grafted stents made out of synthetic material (Dacron or PTFE). Examples of such prior art devices may be found in U.S. Pat. Nos. 5,306,286; 5,026,377; 5,019,085; 5,019,090; 4,913,141; 4,886,062; 4,733,665; and 4,503,569.
In balloon dilatation of vascular stenosis, or blockages, the balloon is inflated within the stenosed vessel, in order to shear and disrupt the wall component of the vessel to obtain an enlarged lumen. This may create a flap or tear at the intima or the media of the vessel wall. The intimal flap can fold down into the lumen and may occlude the vessel. Such occurrences contribute to the high incidence of restinosis which is prevalent. Currently, conventional balloon angioplasty is followed by roughly a 30% to 50% incidence of restenosis.
Vascular prosthetic devices are often utilized in an effort to maintain vessel patency and prevent restenosis. However, vascular prosthetic devices or patches are often associated with increased thrombogenicity of the PTCA site due to the blood contacting the surfaces of the prosthetic device, and result in occlusion of the vessel. Additionally, synthetic materials used in conventional endovascular prostheses tend to reject coverage by the patient""s living tissue, i.e. endothelium, and have collecting surfaces that become thrombogenic sites. Previous biological materials suggested in the art for use in endovascular support have not provided a satisfactory ability to graft to the patient""s tissues. Moreover, the body""s own repair mechanisms can bring progressive stenotic occlusion due to neointimal fibrosis and hyperplasia. Additionally, an immunological response to foreign material can lead to increased inflammation in response to the prosthetic device.
Systemic therapy aimed at preventing coagulation, a thrombosis locally at the graft site, is often complicated at other sites and produces unwanted, even dangerous side effects. Likewise, systemic treatment with growth mediators or chemotherapeutic agents can produce a hyperplastic or hypoplastic response in tissue not specifically targeted. Existing stent devices, such as dip coated stents, providing locally delivered drugs do not satisfactorily promote grafting or integration of the stent into the patient""s endothelium. See for example U.S. Pat. Nos. 5,383,928 and 5,102,417.
Therefore, there exists a need in the art for a device and method for supporting endovascular vessels, which provides local therapy for repairing those blood vessels narrowed or occluded by disease, and which provides a biologically acceptable substrate for grafting to the patient. There is a need for such a device which includes providing local therapy resulting in high local concentrations of therapeutic drugs at the treatment site. The art has sought such an expandable intraluminal vascular support graft, and alternatively an independent arterial-vascular fistula, which prevents recurrence of stenosis, to be utilized to support or replace degenerated vein grafts, coronary arteries, and the peripheral arterial and venous system.
However, prior to the development of the present invention, there has been no expandable intraluminal graft comprised of a biological material which prevents recurrence of restenosis that can also be utilized to deliver drugs locally to the desired location.
The present invention provides an endovascular support device adapted for local delivery of a therapeutic agent and for minimizing the rate of restenosis. The device has a cylindrical support body having an inside surface and an outside surface. The endovascular support device of the present invention also has at least one layer of pericardial tissue covering at least a portion of the inside surface or the outside surface of the cylindrical support body. The endovascular support device of the present invention is provided with a therapeutic agent disposed on a portion thereof.